With the objective of achieving high energy and cooling efficiency, today household and commercial cooling systems use Variable Capacity Compressors—VCC. The characteristics of these compressors are adjustments in the cooling capacity by varying the pumping speed of cooling gas, that is, their mass flow, in accordance with the system requirement and cooling demand.
The variation in the mass flow is from a minimum value to a maximum value, said range of values being proportional to the rotation of the electric motor that drives the hermetic variable capacity compressor. The variation of the rotation is obtained in these compressors by means of an electronic control, called frequency inverter, which adjusts the voltage and the frequency applied to the electric motor.
In general terms, the frequency inverter is provided with various electronic circuits having different functions, such as, for example, a power circuit with input stage for electromagnetic interference filtering and a rectifier bridge stage for converting an alternating current coming from an external power source into a continuous voltage, a control circuit (microcontroller or Digital Signal Processor—DSP), an auxiliary power source for generating internal voltage for other circuits or components of the inverter, a circuit formed by power semiconductors for driving the electric motor employed in the compressor, among others.
It is noted that the electrical connection and fixing of the frequency inverter to the hermetic compressor requires carrying out various steps on the production line. This results in a loss of efficiency and high production and assembly cost of the frequency inverter.
Another problem noted concerns the use of cables for electrical connection between the frequency inverter and the connector, which is generally provided with three pins, of the hermetic compressor. The use of a cable requires the fixing thereof to the printed circuit board of the frequency inverter, which results in increased general costs of production and time, due to the need to solder the cable to the board of the inverter or to use an additional connector on the board.
Additionally, it is noted in the state of the art that the frequency inverter is disposed in a closed plastic box, which is encased mechanically to the support surface (“fence”) of the hermetic compressor, being fastened by means of screws, to meet the standard requirements.
The problems above are noted when carrying out the steps of fixing of the frequency inverter to the support surface (“fence”) of the hermetic compressor, which will be detailed ahead.
The first step is carried out by fixing the components and circuits which make up the frequency inverter on the printed circuit board.
After this step, the connector for feeding the hermetic compressor motor is mounted on the printed circuit board. The grounding connector of the electromagnetic interference filtering circuit (ground connection point) is mounted on the printed circuit board.
The ground branch terminal is pressed in the plastic body of the outer casing.
The printed circuit board is then mounted on the plastic base of the plastic body of the outer casing.
A connection cable of the motor is connected to the connector for feeding the hermetic compressor motor, previously mounted on the printed circuit board. A grounding cable of the electromagnetic interference filtering circuit is connected to the connector positioned on the printed circuit board.
The cable coming from the grounding connector of the electromagnetic interference filtering circuit is connected to the grounding terminal fixed to the plastic body.
The plastic body of the outer casing is mounted on the plastic base, such that the cables previously mounted pass through orifices existing in said body.
The plastic lid is then closed, making interface with the base and the plastic bodies, the lid is screwed to the assembly of base and body, the connector of the cable of the motor is coupled to the connector of the hermetic compressor, a branch of the grounding cable of the electromagnetic interference filtering circuit is coupled to the ground terminal of the compressor, the plastic assembly is encased in the compressor through the orifice existing in the plastic body and the assembly is fixed to the hermetic compressor by means of screws.